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| Relative Velocity in the Case of Two Velocities Inclined to Each Other |
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The figure above shows two cars moving
with velocities
 inclined
to each other at an angle q. Let the relative
velocity of
with respect to  . |
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| However, from the parallelogram of vectors OABC, |
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| In a similar way, the relative velocity VA with respect to VB, that is, VAB can also be determined. The figure below illustrates this case. It can be seen that the magnitude of relative velocity in both cases is the same with the direction reversed. |
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| 1) When both the cars are moving in the same direction, i.e., q = 00 degrees. |
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| Thus, the relative speed between two bodies moving in the same direction is equal to the difference of the individual speeds of two bodies. |
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| 2) When the two cars are moving along parallel lines in opposite direction, i.e., q = 1800 degrees. |
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| Then |
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| However, relative speeds cannot be negative. |
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| i.e., the relative speed between two bodies moving in opposite directions is equal to the sum of the individual speeds. |
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| This is an example in which a man can hold his umbrella properly by making use of the concept of relative velocity. |
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The figure above shows a man walking due
east with a velocity
 .
The rain is falling vertically with a velocity
 .
The relative velocity  of rain w.r.t the man is calculated in the
following way. |
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| Applying the law of triangle of velocities. |
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| Moreover, tan q = Vm / Vr which gives the angle at which the man can hold his umbrella with the vertical, in order to protect himself from the rain. |
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